Roadway construction



' a superficial surface of the pavement.

Patented Aug. 16, 1927.

PATENT OFFICE.

AUGUST E. SCHUTTE, OI NORTHBORO, MASSACHUSETTS.

noAnwAY CONSTRUCTION.

IojDrawing.

My invention relates to a method of securing and cementing thin roadwaysurfaces to their foundations such as Portland cement concrete, brick orother material, and is especially designed to re-surface concreteroadways. The invention resides primar ly in a method of rendering theconcrete or other surface receptive and retentive of a bituminouscoating upon which then can be placed, if desired, a bituminous wearingsufface, or the first and original bituminous layer can be used alone.

It is a well known fact that concrete road surfaces after having been inuse for a while become scaly and uneven on account of p-ar ticles orsmall areas breaking off. Many attempts have been made to renovatesuchsurfaces in various ways and especially by applying bituminous compoundssuch as tar,

asphalt and the like. All these attempts have beenunsuccessful. This isprimarily due to two factors.one isthe moisture inherent in a porousconcrete structure, and the other is dust which is always presentfonbituminous material is placed upon such con-' crete surface, themoisture absolutely revents adhesion and if the upper surface should bedry, it is always more or less covered with dust which it is impossibleto remove, and which prevents the penetration of the bitumen sothat uponchilling it-scales off and is removed by traific. If the bituminousmaterial placed upon such a surmitting the thin oils to penetrate to ashort distance, leaving the'heavier oils, at the sur face. In such acase the bituminous layer is only held temporarily for the thin :oilpenetrates deeper and deeper into the structure,

leaving the heavier medium resting on the A, I surface, so that after ashort time it scales take place: First, the asphalt so heated be-v comesvery. fluid and penetrating, easily and rapidl entering the pores of thestructure.

Secon the execessive heat of the penetrata lication filed ma 29,

face is of a thin and oily-nature, the dust P and the structure itselfacts as a filter, per- 7 1922. Serial No. 578,502.

ing asphalt evaporates the moisture at the immediate surface ofthe'roadway and-it escapes throu h the thin, limpid asphalt. Since thesur ace of the asphalt on the concrete structure is very thin, thebubbles formed by the vapor or steam easily burst and allow the steam toescape, while the heat still applied at the surface kee s the asphalt soliquid that it immediately fills the space left by the bursting bubbleand forms a continuous thin asphalt surface which is thus keyed to theconcrete structure itself and on hardening forms a non-scalable, bi-

' tum-inous surface.

The bituminous surface thus formed is naturally retentive of anybituminous struc Y ture subsequently placed upon its to' so that it canbe thickened to any desired thickness by applying upon it by anysuitable means more asphalt composition, or an asphalt compositioncontaining a large percentage of asbestos fibre to toughen itsuch as isdescribed in my U. S. Letters Patent No. 1,265,259, dated May 7, 1918,or any other suitable tough bituminous 1ayer..

It is a well known fact among engineers and road builders that the wearof a bituminous roadway depends to a great extent upon the bitumencontent in the mixture, i. e.

the same grade of asphalt beingused, a

mixture containing a: greater amount of such asphalt will bea mixturewhich will wear longer and better than one .hav'ing less asphalt,provided the mixture can be kept in lace and prevented from shoving andrutting. It has been impossible heretofore to use such rich thinmixtures because no'me'ans were found to anchor them to the foundationso that they naturally were shoved and broken up by trafic i If againsuch rich mixtures were laid thick, while they would resist abrasion,they would not-resist the dead weight of traffic and soon formed rutsand channels and became useless.

With my method of anchoring such coatin s securely to a rigid concretefoundation, it is possible thereby to cement them to such foundationsand'so to cover the foundation with a very tough, thin layer ofbituminous compound, containing fibres like asbestos, with or withoutthe'addition of mineral matter, and thereby produce an excellentroadway. Old'concrete roadways can thus be renewed andold bitumlnoussurfaces canbe toughened, revived and leveled. Not only is crete by mymethod, but the concrete itself is toughened and strengthened at thepoint of contact bybeing cemented at the line of juncture by twocements, a: concrete and bituminous.

I To practice my invention I proceed as folows-:--

Assuming that an old concrete road is to,

, pores, crevices and voids on the side of the cracks. The Whole surfaceis then treated by spreading bitumen, either in a liquid form or in theform of powder or chunks, and applying intense heat,heat which will meltthe bitumen and raise it to a tempera ture above its flash point, suchthat it may cause the surface being treated to burst into flame,liquefying the asphalt, evaporating the moisturein the concrete andpenetrating into it. The distance of penetration depends upon thelengthof application of the heat, but for paving surfaces the lightpenetration of a sixteenth of 'an inch or. so is suflicient to secureadhesion, and this can be achieved in a few minutes. The means ofheating can be-either direct flames, which is the simplest way, or canbe superheated steam, superheated air, gas or any other suitable meansfor producing intense heat.

- After. the surface has thus been treated, it

is found that some of the asphalt has penetrated moreor less into thestructure, leav-- ing the most of it on the surface as a con.- tinuousthin layer. Such treatment alone is sufficient for surfaces exposed topedestrian traflic, such as sidewalks and especially fac tory floors.For street roadways, however, it is preferable to thicken thisbituminous surface. A hot bitumen will stick, adhere to, becomecommingled with and be retained by a bituminous surface. Therefore tothicken the layer of bitumen on the treated concrete surface, it is onlynecessary to apply a secondary coating of a rich bituminous mixture at atemperature hot enough to melt or. soften the bitumen below, so that thetwo layers will coalesce. This secondary coat, if such is used, ispreferably one composed of asphalt, having incorporated therewith shortabsestos fibre and, if desired, some sand, and applied at a heat ofabout 350 degreesFahrenheit; or a rich mixture of sand and bitumen canbe applied or, in fact, any rich, tough, bituminous com osition. Thesecan be troweled on or p aced there by any suitable machine and afterbeing slightly chilled, are treated with a superficial scattering ofclean sand, which will not penetrate the structure itself, but will lieon the top and be slowly impressed into the surface'by-trafiic, givingthe structurea gritty, sand-paper-like surface.

While my invention relates especially to the repair of concretesurfaces, it may be used with such surfaces when freshly laid,

or in fact with any surfaces to which it is necessary to bind abituminous layer. In using the term roadway I mean to include anywearing surface subject to travel of any kind such as highways,sidewalks, floorings, etc., and in using the term foundation I mean thesurface which receives the bituminous coating and to which such coatingis to be united, whether it be-made of concrete, bitumen or othermaterial, for the essence of my invention relates to the maintaining ofthe coating ata temperature approximately or above its flash point,Whereby its temperature will effect a penetration of the foundation bythe coating or the intermingling of the two so that they are tiedtogether.

What I claim as my invention is 1. That method of uniting a bituminouscoating to a concrete roadway surface which consists in applying saidcoating to said surface and raising it to a temperature. approximatingits flash point and maintaining it at such temperature for a shortperiod of time whereby a portion of it will penetrate said surface andthe remainder will form a protective coating therefor. 1

2. A method of adding a. bituminous layer to a concrete surface whichconsists in heating the concrete, applying a bituminous compound such asasphalt, heating said asphalt to its flash point whereby it will enterthe poresand evaporate the moisture, and then applying a secondarywearing surface thereto.

AUGUST E. SCHUTTE.

